Hoe do I tell if the weed is really dank????

Actually dank is a word that refers to moisture. It's usually referring to cellars, as in "That's a pretty dank cellar". Most likely it was taken as slang to mean good buds.

I dont care what dank used to mean but to me dank be chronic
and chronic bud smells like nothing else
weed can always look good so yes
the best way to tell is to smoke it.
but you're mainly looking for crystals
most good bud will have alot of sticky crystals!!!

It should be damp, but doesn't have to be.

Basically, just look for crystals.

smell, too- stronger smelling shit, at least I've found, tends to indicates stronger bud in general.